1. Field of the Invention
This invention relates generally to methods of producing hydrocarbons from wellbores formed in subsurface formations and more particularly to apparatus and methods for regulating and/or equalizing production from different zones of a wellbore to optimize the production from the associated reservoirs or pay zones.
2. Background of the Art
To produce hydrocarbons from earth formations, wellbores are drilled into reservoirs or pay zones. Such wellbores are completed and perforated at one or more zones to recover hydrocarbons from the reservoirs. Horizontal wellbores are now frequently formed into a pay zone to increase production and to obtain on the aggregate higher quantities of the hydrocarbons from such reservoirs.
Sand screens of various designs and slotted liners are commonly placed between the formation and a tubing (production tubing) in the wellbore, which transports formation fluid to the surface to prevent entry of sand and other solid particulates into the tubing. Screens of different sizes and configuration are commonly used as sand control devices. The prior art screens typically erode substantially over time. The present invention provides a screen which is less susceptible to erosion compared to prior art screens.
Excessive fluid flow rates from any production zone can cause, among other things, excessive pressure drop between the formation and the wellbore casing, relatively quick erosion of inflow devices, water or gas coning, caving, etc. Therefore, to avoid such problems, fluid flow from each production zone is controlled or regulated. Several flow control devices have been utilized for regulating or controlling production of formation fluids. One recent device passes the formation fluid through a spiral around a tubular to reduce the pressure drop before the fluid is allowed to enter the tubing. The spiral provides a tortuous path, which can be plugged at one or more places to adjust the fluid flow from the formation to the tubing. This device, although effective, must be set at the surface prior to its installation. U.S. patent application Ser. No. 08/673,483 to Coon, filed on Jul. 1, 1996, and assigned to the assignee of this application, discloses an electrically operable sliding sleeve for controlling fluid flow through a tortuous path. This sliding sleeve may be operated from the surface. U.S. application Ser. No. 08/673,483 is incorporated herein by reference. The present invention provides a flow control device that can be opened, closed or set at any intermediate flow rate from the surface. It also includes multiple fluid paths, each of which may be independently controlled to control the formation-fluid flow into the tubing.
In vertical wellbores, several zones are produced simultaneously. In horizontal wellbores, the wellbore may be perforated at several zones, but is typically produced from one zone at a time. This is because the prior art methods are not designed to equalize flow from the reservoir throughout the entire wellbore. Further, the prior art methods attempt to control pressure drops and not the fluid flows from each of the zones simultaneously.
The present invention provides methods for equalizing fluid flow from multiple producing zones in a horizontal wellbore. Each production zone may be independently controlled from the surface or downhole. This invention also provides an alternative system wherein fluid flow from various zones is set at the surface based on reservoir modeling and field simulations.